1. Field of the Invention
This invention relates to cation exchange membranes, and more particularly to improved cylindrical cation exchange membranes for use in electrolysis of an aqueous alkali metal chloride solution in a finger type electrolytic cell.
2. Description of the Prior Art
The term "finger type electrolytic cell" as used herein includes an electrolytic cell of flattened tube-type construction as well as an electrolytic cell of finger type construction as described in J. S. Sconce, CHLORINE--ITS MANUFACTURE, PROPERTIES AND USES, Reinhold Publishing Corp., New York (1962), page 93.
Cylindrically molded cation exchange membranes are suitable for fitting into finger type electrolytic cells. However, cylindrically molded cation exchange membranes often provide electrolytic products having higher levels of impurities (e.g., alkali metal chloride) than the products obtained from a filter press type electrolytic cell, even if electrolysis is conducted using membranes with the same performance (i.e., the same properties of the membranes) and the same current density
One of the reasons for this is that the areas of cathode, membrane and anode are nearly equal to each other in the filter press type electrolytic cell, whereas the area of membrane is larger than that of anode in the finger type electrolytic cell. Since the average current density of the membrane is lower than that of the anode, and low current density areas are present in localized areas of the membrane, and the concentration of alkali metal chloride in the alkali metal hydroxide formed is high.